Dynamics of a quantum two-state system in a linearly driven quantum bath

TL;DR

This paper explores how a quantum bath driven by external pulses influences a two-level quantum system's relaxation, revealing new resonances and effective forces that depend on the bath's spectral features.

Contribution

It introduces the concept of a driven quantum bath affecting a non-driven two-level system, highlighting the emergence of new resonances and effective forces.

Findings

Driven bath induces a time-retarded effective force on the system.

Structured Ohmic bath shows additional resonances similar to Jaynes-Cummings spectrum.

Response depends on the spectral characteristics and history of the bath perturbation.

Abstract

When an open quantum system is driven by an external time-dependent force, the coupling of the driving to the central system is usually included whereas the impact of the driving field on the bath is neglected. We investigate the effect of a quantum bath of linearly driven harmonic oscillators on the relaxation dynamics of a quantum two-level system which itself is not directly driven. In particular, we calculate the frequency-dependent response of the system when the bath is subject to a Dirac and a Gaussian driving-pulse. We show that a time-retarded effective force on the system is induced by the driven bath which depends on the full history of the perturbation and the spectral characteristics of the underlying bath. In particular, when a structured Ohmic bath with a pronounced Lorentzian peak is considered, the dynamical response of the system to a driven bath is qualitatively different as compared to the undriven bath. Specifically, additional resonances appear which can be directly associated to a Jaynes-Cummings-like effective energy spectrum.